This invention relates to a hub clutch assembly mounted to each front wheel of a four-wheel drive vehicle for changing over between transmission and cutoff of the driving force between the axle and the wheel hub and, more particularly to an arrangement for mounting a gasket used to airtightly close an end of the wheel hub with a cover, and to an arrangement for mounting a seal for shutting off two fluid passages for changeover between transmission and cutoff of the driving power.
In a part-time four-wheel drive vehicle, hub clutches are mounted between the front wheel hubs and the axle to change over the state of transmission of the driving force to the wheels.
FIG. 7 shows a hub clutch assembly 1 that utilizes air pressure for changeover of driving force. A spindle 3 is fitted on a front wheel axle 2 and fixed to a vehicle knuckle while rotatably supporting a wheel hub 5 through a bearing 4.
An inner ring 6 as a driving member of the hub clutch assembly 1 is axially slidably but relatively nonrotatably mounted on the front wheel axle 2 at its tip by serrations 7. The inner ring 6 has an external gear 8 on its outer periphery. An outer ring 9 as a driven member is rotatably mounted around the inner ring 6. The outer ring 9 is relatively nonrotatably mounted in a cover 11 fixed to an end of the wheel hub 5 by a plurality of bolts 10. The outer ring 9 has an internal gear 12 in its inner periphery with which the external gear 8 is adapted to move into and out of meshing engagement.
The end face of the wheel hub 5 is closed by the cover 11 tightened by the bolts 10 through a gasket 13. The interior of the cover 11 is kept airtight by a sleeve 26, diaphragm 14, and a yoke 24'. The diaphragm 14 is secured by the sleeve 26 and the yoke 24'. The diaphragm 14 has its inner edge coupled airtightly to the inner ring 6 so as to be axially movable with the inner ring 6. The interior of the cover 11 is thus divided into airtight chambers 15 and 16 by the diaphragm 14. The gasket 13 prevents the entry of water and air into the cover, thus keeping the interior of the cover airtight.
A spring 17 is mounted in a compressed state between opposed surfaces of the diaphragm 14 and the cover 11, biasing the inner ring 6 toward its rearward position. A magnet 19 is fixed through a case to the inner side of the cover 11 at its center to attract a washer 18 for fixing the diaphragm 14 when the inner ring 6 is in its forward position and, thus keeping the external gear 8 away from the internal gear 12.
To move the inner ring 6 for controlling changeover between the two-wheel drive state and the four-wheel drive state, air passages 20 and 21 are provided so as to communicate with the respective airtight chambers 15 and 16, respectively.
The first air passage 20 communicating with the outer airtight chamber 15, is comprised of a passage 20a formed in the cover 11 so as to communicate with the airtight chamber 15, a gap 20b defined between the spindle 3 and the wheel hub 5, a space formed in the bearing 4 mounted in the gap 20b, and a passage 20c formed in the rear portion of the spindle 3. An air pipe 20d connected to the passage 20c is connected to an air source.
The second air passage 21 communicating with the inner airtight chamber 16, is comprised of a gap 21a between the axle 2 and the spindle 3, and a passage 21b formed in the rear portion of the spindle 3. An air pipe 21c connected to the passage 21b is connected to the air source.
The airtight chambers 15 and 16 are kept airtight by a seal 23 fitted in the cover 11 and pressed against a nut 22 tightened onto the tip of the spindle 3. Since the first air passage 20 is provided between the spindle 3 and the wheel hub 5 and the second air passage 21 is provided between the front wheel axle 2 and the spindle 3, spaces and gaps in the wheel hub 5 can be used as parts of the air passages. This leads to a reduced diameter of the entire hub clutch assembly 1.
For changeover to the four-wheel drive mode, the inner ring 6 is moved inwardly to mesh the external gear 8 with the internal gear 12.
The front wheel axle 2 and the wheel hub 5 are thus directly coupled together (for four-wheel drive mode), and also the engine braking force can now be delivered to both front and rear wheels.
For changeover from four-wheel to two-wheel drive mode, air in the outer airtight chamber 15 is sucked out to create a pressure difference on both sides of the diaphragm 14. This pressure difference pulls the diaphragm 14 outwardly together with the inner ring 6 against the force of the spring 17 until the diaphragm fixing washer 18 is attracted by the magnet 19 toward the cover 11, thus separating the external gear 8 from the internal gear 12 as shown in FIG. 7.
Thus, the hub clutch assembly 1 can be changed over between the the two-wheel and four-wheel drive modes by applying a negative pressure or a positive pressure in one of the airtight chambers 15 and 16 on both sides of the diaphragm 14. The two-wheel drive mode is maintained with the magnet 19 attracting the diaphragm fixing washer 18 toward the cover 11. The four-wheel drive mode is maintained by the force of the spring 17.
The gasket 13 is provided between end faces of the wheel hub 5 and the cover 11 to prevent air leakage. Heretofore, the gasket 13 was bonded to the end face of the cover 11 when the component parts of the hub clutch were mounted in the cover. The hub clutch assembly thus formed was delivered to a car manufacturer.
Bonding of the gasket to the cover constitutes a separate step from other assembling steps. Thus, this step impairs assembling efficiency.
An object of this invention is to provide a hub clutch which needs no bonding of the gasket to the cover and thus can be assembled with higher efficiency.
The seal 23 provided between the two passages leading to the respective airtight chambers to prevent air leakage between the two passages comprises a core member 25 having such an outer diameter that it can snugly fit in the cover 11 and having a ]-shaped section, and a seal member 24 fixed to the inner edge of the core member 25 in slide contact with the outer periphery of the nut member 22 threaded onto the spindle 3. The core member 25 meshes with the inner periphery of the cover 11 and bears against the outer ring 9 while the seal member 24 is in slide contact with the nut member 22 to shut off the passages 20 and 21 from each other.
Since the core member 25 simply engages the inner periphery of the cover 11, it has neither the function of preventing the rotation of the seal relative to the cover 11 nor the function of axially positioning the seal. Thus, the seal tends to shift, resulting in poor sealing for shutting off the passages 20 and 21 from each other.
Another object of this invention is to provide a hub clutch assembly which can hold the seal in position relative to the cover, thus maintaining the sealing function with high reliability.